Cathode ray control apparatus



M 1a, 1941. R, RT L 2,235,053

CATHODE RAY CONTROL APPARATUS Filed July 24, 1937 7'0 W050 J/G/VAL SOURCE DFFZECT M 6 ENERGY INVENTOR RUDOLF TEL ATTORNEY Patented Mar. 18, 1941 UNITED :srAre-s OFFICE 'Iunken Gesellschaft fiir nrahtlose Telegraphic m. b. 11., :Berlin, Germany, a corporation f Germany 7 Application July'24, 1937,"Seria'l'No.'l55;398 In Germany August :12, 1936 s-claims. (01.25'0-27) My invention relates broadly to cathode 'ray control apparatus and more particularlyto "apparatus 'for'blocking the potential of: the ray during its return stroke. i

In my co-pending' application Serial No;' 80,'984,

filed May 21, 1936, Patent No.'2,202,"612, dated May 28, 1940, there hasbeen -disclosed a circuit arrangement for Braun television receiver tubes operating with deflection coils in -which the cathode ray beam after completion of each line and after completion of eachirame oreach set or series of lines is blockedo'utas-a functionof the returnor flyback action of the deflection circuit of the receiver. For this purposagenerally speaking,'a potentiometer is "connected in parallel relation to the deflector coils through a'condenser in such a way thataportionofthe .potential arising across the-potentiometerandxofa polarity which will block out'the cathode :ray pencil is impressed on the modulation circuit of the Braun tube. More particularly speakingthe arrangement disclosed'in my'copending application is chosen in sucha way that the tap of a potentiometer is =unitedwiththe cathode of the Braun tube and the intensityor modulation control means is joined totheiend ofthe potentiometer opposite or awayfrom the coupling condenser joining the potentiometer tothe deflecting means of the tube. However, the aim of this circuit may under certain circumstances be vitiated by self-capacitance inherent in the assembly, more especially'by'the capacity to ground 7 of the cathode of the cathode ray tube. v

Now, in order to overcome the said diiiiculty and to thus make the said circuit "arrangement useful and suited for any kind of construction of the Braun tube, according'to this invention, the potentiometer turned to the deflector coiland/ or the part thereof from which the blocking potential is derived has a condenser connectedin parallel to it. In this manner conditions are made so that the potential between the brightness control or modulation means of the Braun tube and its cathode, during the flyback or return action of the deflection circuit, will have the same trend or polarity as the voltage at thedefiection coil itself. In fact, by choosing suitable dimensions for the condenser it may even be feasible to make conditions so that the voltage at the Braun tube as stated, save for a proportionality factor, will be exactly the same as the potential across the coil. However, in order to insure such equality of potentials another condenser may be connected in parallel also to the part of the potential' divider from which" the blocking potential fortheBraun tube is tapped.

invention-:will, .best' be understood by refer ence to the drawing inwhich center tap of a potentiometer 21, 28 which is grounded at one end througha biasing potential source 25. Theend of the potentiometer remote fromthat extremitywhich is grounded is joined through --a condenser 26' to the deflecting coils 'o'fthe tube-andat *the-"end'o'f the coils remote 'fr'om'the-end-joined tothe-condenser 26, there is joined a' biasing -battery I 22 one side -of-which is grounded. z

Qneembodiment of the invention shall be explained inmore'detail by reference to the accompanying drawing, and:it'shall also be explained themannerinwhich the self-capacitances of the circuit arrangements :act and how :their troublesome effect is wpreventable.

Referring to the drawing, III, II denote .a deflector coil, say, for the line deflection means, while l2.is 'theBraun .tube; .l3r'isea sourceof D. C. supply which furnishes-the coilwcurrent. A voltage divider comprising-resistances I5, I6 is connected with the coils 10,. H through a condenser M. The tap P .of':the said-potentiometeris connected with the -cathode l'l :ofthe Braun tube I2, while the end ithereofxin'dicatedat Eremote from the condenser M 1sconnectedwith the grid or intensity modulator device l8. Included in thisconnection is the secondary :winding of a-transformer [9 by means "of which the-brightness control impulses are :ied zito'a the intensity control or modulating electrode .of theiBra'untube. Also included therein -optionallywis an C. source of potential 20 which impresses a negativebiasing potential upon the brightness control or modulating electrode. The condenser 2| which is to be provided according to this invention shall be discussed further below.

Among such undesirable capacitances as will arise in a circuit organization as here illustrated, the capacity to ground of the cathode 11 plays the chief part, particularly in the case of indirectly heated tubes. This condition is indicated by condenser 22 and its connection (leads) indicated by the dotted lines. Now, if during the releap of potential at point L are drained or leak away to ground through condenser 22 and will thus cause no fall of potential across the resistance it. But if, according to the invention, condenser 2] is connected in parallel relation to the resistance [5, then, if the said condenser is conveniently balanced and proportioned, conditions can be so shaped that the potential arisingat point L will be divided by the voltage divider-2|, 22 in the samerelation as by the resistance l5 and It. In other words, the shape of potential at point P, even if the balance were not quite a'ccurate, will at any rate come quite closeto that at point L, while if the balance is exact, the poten tial will turn out strictly the same, save for a factor of proportionality. I I

Unless the self-capacitance of resistance [5 is appreciable, the desired potential relations may be established by connecting a condenser in par-1 allel to the resistance I6. Under certain 'circumstances it may be found advantageous to dispose a condenser to each of the two resistances l5 and I5.

WhatI claim is:

1. A return line elimination system for cathode ray tubes comprising a cathode-ray tube including modulating and cathode electrodes, said latter electrode having a definite capacity with respect to a reference section, deflecting means for said tube, a series electrical circuit comprising ,said defiecting means and a potentiometer, said potentiometer being electrically connected to said reference section, means connecting the modulating electrode of said tube to said potentiometer and said reference section, means connecting the cathode of the cathode ray tube to a point on said potentiometer and a condenser .shunted across the portion of said potentiometer external to the portion thereof connected in the modulating electrode-cathode circuit of said cathode ray tube to substantially compensate for; the capacity of the cathode with respect to the reference section. l

2. A return line elimination system for'cathode ray tubes comprising a cathode ray tube including modulating and cathode electrodes, said latter electrode having a definite capacity with respect to a reference section, deflecting means for said tube, a series electrical circuit comprising said deflecting means, a condenser, a potentiometer and a source of energy, said seri'es circuit being electrically connected to said reference section, means connecting the modulating electrode of said tube to said potentiometer and said reference section, and a condenser shunted across the portion of said potentiometer-external to the portion thereof connected in the modulating electrodecathode circuit of said cathode ray tube to substantially compensate for the capacity of the cathode with respect to the reference section.

3. A return line elimination system for cathode ray tubes comprising a cathode ray tube including modulating and cathode electrodes, said latter electrode having a definite-capacity with respect to aground, deflecting means forSaid tube, a series electrical circuit including said deflecting means and a potentiometer, said series circuit being electrically connected to said ground, means connecting the modulating electrode of said tube to said potentiometer and said ground, means connecting the cathode of the cathode ray tube to a point on 'said potentiometer and a condenser shunted across th'eportion of said potentiometer external to the portion thereof connected in the modulating electrode-cathode circuit of said cathode ray tube to substantially compensate for the capacity of the cathode with respect to the reference section.

4. A return line elimination system for cathode ray tubes comprising a cathode ray tube including modulating and cathode electrodes, said latter electrode having a definite capacity with respect toa ground, deflecting means for said tube, a series electrical circuit comprising said deflecting means, a condenser,a potentiometer and a source of energy, said series circuit being electricallyconnected to said ground, means connecting the cathode of the cathode ray tube to a point on said potentiometer, means connecting the modulating electrode of said tube to said potentiometer and said ground, and a condenser shunted across the portion of said potentiometer external to the portion thereof connected in the modulating electrode-cathode circuit of said cathode ray tube to substantially compensate for the capacity of the cathode with respect to the referencesection.

' 5. A return line elimination system for oath ode ray tubes comprising a cathode ray tube including modulating and cathode electrodes, said latter electrode having a definite capacity with respect'to a reference section, deflecting means for, said tube, a series electrical circuit including said deflecting means and a potentiometer, said series circuit being electrically connected tosaid reference section, means connecting the modulatin electrode ofsaid tube to said potentiometer and saidreference section, means connecting the cathode of the cathode ray tube to a point on said potentiometer and a condenser shunted across the portion of said potentiometer external to the portion thereof connected in the modulatingelectrode-cathode circuit of said cathode ray tube tosubstantially compensate for the capacity of the cathode with respect to the reference section, said latter condenser being of such value whereby the shunting of pulses normally shunted through the capacity between the cathode and reference section is substantially eliminated.

RUDOLF URTEL. 

